The present invention relates to an electric steering device for assisting a steering operation of a vehicle.
An electric steering device has been known which generates a steering assist force using an electric actuator for assisting a steering operation, that is, an operation of a steering wheel of a vehicle.
As the electric steering device is driven by electric power, driving of the electric steering device is stopped when a power supply system of a vehicle is turned off. When driving of the electric steering device is stopped, as a driver performs a steering operation without a steering assist force, the steering operation is required to be performed with a larger force than usual.
A patent literature 1 discloses a technique which includes a detection unit for detecting a turning-on/off of a power supply switch of a vehicle and a determination unit for determining whether or not a running speed of the vehicle is lower than a predetermined speed. In this technique, in a case that the detection unit detects the turning-off of the power supply switch, power supply to a steering device for the vehicle is stopped only when the determination unit determines that the running speed is lower than the predetermined speed.
[Patent Literature 1] JP-A-2000-128009
In this related art, for example, even in a case that the power supply switch is erroneously turned off during running of the vehicle or the detection unit for detecting a state of the power supply switch becomes failure, it is possible to continuously drive the steering device for the vehicle to generate the steering assist force similar to that in the normal state. Thus, if the aforesaid erroneous operation, failure or the like occurs, it is possible to avoid occurrence of such a phenomenon that a steering wheel suddenly becomes heavy, that is, a force required for operating the steering wheel suddenly becomes large, during running of the vehicle and hence the steering operation becomes difficult.
However, the aforesaid related art has a problem that the driver is hard to notice the erroneous operation or failure.
Therefore, the invention, having been contrived bearing in mind the heretofore described circumstances, has for its object to provide an electric steering device which enables a driver to easily notice an erroneous operation with respect to a vehicle and a failure of a power supply system while maintaining steering performance of the vehicle.